Cetus

Overview

Cetus is a constellation in the southern sky. It is named after Cetus, a sea monster in Greek mythology, although it is often called 'the whale' today. Cetus is located in the region of the sky that is water-themed and is surrounded by other aquatic constellations, including Pisces (the fish), Eridanus (the river), Piscis Austrinus (the southern fish), and Aquarius (the water bearer).

A dark sky with stars forming the shape of Cetus constellation

History and Mythology

Cetus has been recognized as a constellation for many centuries, with its first known documentation appearing in the 2nd century in Ptolemy's Almagest. In Greek mythology, Cetus was a sea monster, sometimes referred to as 'the whale' or 'the sea monster of Poseidon'. The constellation was visualized as the monster that was sent by Poseidon to destroy the city of Ethiopia as punishment for Queen Cassiopeia's boast that her daughter, Andromeda, was more beautiful than the Nereids.

Notable Features

Cetus covers 1231 square degrees, making it the fourth largest constellation in the night sky. It contains several notable features, including a number of stars with known planets, and the famous variable star Mira (omicron Ceti). Mira was the first variable star to be discovered and remains the prototype of its class, the Mira variables.

Another notable feature is the barred spiral galaxy Messier 77, one of the brightest galaxies in the sky. It is also home to the Cetus Dwarf, a small elliptical galaxy that is a satellite of the Milky Way.

Stars

Cetus contains several bright stars that make up its characteristic shape. The head of Cetus is marked by the star Beta Ceti, also known as Diphda or Deneb Kaitos. Other notable stars include Alpha Ceti (Menkar), Gamma Ceti (Kaffaljidhma), and Tau Ceti. Tau Ceti is of particular interest as it is one of our nearest cosmic neighbors and has a system of at least five planets.

Deep Sky Objects

In addition to its stars, Cetus also contains a number of deep sky objects. These include the aforementioned Messier 77, as well as the spiral galaxy NGC 247, the irregular galaxy IC 1613, and the Cetus Ring, which is a ring galaxy.

Visibility

Cetus is visible at latitudes between +70° and -90°. It is best visible at 9 p.m. during the month of November.